The study by Boston Consulting Group (BCG) identifies a shift from "owning a luxury to experiencing a luxury" with bespoke treats now accounting for more than half of the $1.4tn spent on luxury goods and services last year.

Luxury sales have boomed in the last two years as the industry recovered from the hiatus caused by 2008 global financial crisis, which provoked a sharp fall in conspicuous consumption.

The sector has also been buoyed by the growing number of millionaire shoppers in markets such as China and Brazil, who are picking up the slack as consumers in traditionally important luxury markets such as western Europe, Japan and the US continue to spend more cautiously.

"The gap in income inequality is growing, which is unfortunate, but there are more and more millionaires every year," said Jean-Marc Bellaiche, a BCG senior partner who heads the firm's luxury practice.

"They do not want to own new things, so are the primary customers for experiential luxury offerings," he said. Their options are not limited to exclusive safaris and spas, they can book themselves in for a five-star hospital stay where they will be waited on by a butler and the en suite facilities include a marble bath.

The business of providing luxury experiences – from art auctions to exclusive travel packages – is now worth $770bn, according to the study. BCG predicts a 7% increase in luxury spending this year, albeit at a slower rate than the industry has enjoyed in the last two years.

Stock markets around the world have been shaken since April as the eurozone crisis, the faltering US economic recovery and signs of a slowdown in China, have made some analysts take a more cautious view of the outlook for luxury sales.

Recent upsets include last week's decision by luxury jeweller Graff Diamonds to scrap its $1bn Hong Kong flotation after a lacklustre response from investors. Rival jeweller Tiffany, which is considered a key barometer of health for the luxury consumer, did not helped Graff's cause by cutting its sales and profit forecasts in the days leading up to the planned listing.

Despite these fears, BCG says the growth of the middle class in emerging markets such as China, Brazil and Russia will boost the global luxury market. Big cities in the these nations are becoming powerful luxury hubs and their residents are a shopping force abroad, with the group dubbed "international travelling consumers" making their presence felt in the boutiques of shopping destinations such as London and Paris.

Affluent Brazilians, for example, are making an impact far beyond their own shores, bolstering property markets in Florida and buoying luxury retailers in Miami and New York. "If there are [fewer millionaires], and if there is a big slowdown in China or Brazil, this will impact the sector," said Bellaiche. But he added: "The reservoir for growth still exists."

With China on track to become the world's biggest luxury market by 2015, the growing might of its consumers, both at home and abroad, means it is expected to remain a potent force in the luxury goods market.

BCG says that by 2020, 330 Chinese cities will have the same level of disposable income that Shanghai had in 2010. "And Shanghai today is clearly a city of luxury like London or New York," said Bellaiche.